Abstract: A method for screening fibrous stock slurry having a rotor impeller and a screen, in which accepts quality and throughput may be adjusted without stopping the screening process by relative displacement of the clearance between the rotor and the screen plate. In one version, this relative displacement is accomplished by axial displacement of frusto-conical portions of the bladed rotor and screen. The relative axial displacement changes the degree of pulp disturbance in a primary screening zone, thus causing throughput and accepts quality to change accordingly. The primary screening zone may be between the rotor impeller and the screen, or it may be on the other side of the screen, in which case the blades on the screen are designed to permit a portion of the pulp slurry to flow through the screen into a region between the rotor impeller and the screen.

Abstract: A dam is used to divide the typical single screen of a fibrous stock screening apparatus into two primary screening zones. Stock inlet and rejects outlet ports are routed to each primary screening zone. The screen is extended past the typical rotor to create an initial screening zone. One or more of the blades of the rotor may also be extended to create turbulence and/or oscillating pressures in the initial screening zone. The profile of the blades may be designed to produce a shearing action with a long moderate relief on the trailing edge to create gradual and extended negative pressure.

Abstract: An apparatus for screening fibrous stock. The apparatus includes a preliminary screen, a rotor, and a cylindrical secondary screen. The stock first passes through the preliminary screen into the rotor and secondary screen. The preliminary filtered stock then passes through the secondary screen. Any stock not passing through the preliminary or secondary screens is discharged from the apparatus.

Abstract: Baffles are added to the blade members of the rotor of an apparatus for screening fibrous stock to cause the flow of stock within the screening zone along the length of the blades to angle away from the blades rather than parallel with the blades. Passageways are added to allow untreated stock to be added at points deep within the screening zone to maintain a proper water to fiber ratio throughout the screening zone.

Abstract: An apparatus for screening fibrous stock. A rotor is rotatably mounted within an open ended, cylindrical screen which is mounted in a hollow housing. Fibrous stock is introduced into the housing and rotation of the rotor causes the portion of the fibrous stock that will pass through the screen to do so. Any fibrous stock that passes through the screen is discharged from the housing. The rotor includes a cylindrical body member having a plurality of blade members attached thereto and spaced substantially evenly about the circumference of the body member and radiating outwardly therefrom. Each blade member has a leading edge and a trailing edge with the leading edge spaced farther from the body member than the trailing edge.

Abstract: An apparatus for sorting wood chips or other particulate material into groups according to size. The apparatus includes a housing having an opened top, a first screen attached to the housing substantially covering the opened top thereof, a second screen attached to the housing beneath the first screen, and a hopper fixedly attached to the housing for holding a quantity of wood chips and for depositing wood chips onto substantially the center of the first screen. The first and second screens slope downwardly from the centers thereof so that any wood chips of a size too large to pass therethrough will pass, aided by the force of gravity, to the periphery thereof.